In the absence of a HIV vaccine, and with inconsistent use of condoms, the AIDS pandemic continues to gather momentum. Sexual exposure is the primary route of infection with women becoming disproportionately affected. In this setting, there is an urgent need to develop new female controlled prevention technologies including microbicides. Ideally, microbicides should provide protection against HIV-1 and other common sexually transmitted infections (STIs) such as herpes simplex virus (HSV) and human papilloma virus (HPV). These products should be safe, effective, acceptable and cheap to manufacture. They should also be able to be used in both the vaginal and rectal compartments. The purpose of this grant is to use aptamer technology to generate individual candidate microbicides with activity against HIV-1, HSV-2 and HPV-16. HSV-2 and HPV-16 have been chosen because they are known to increase the risk of HIV-1 transmission (HSV-2) or are linked to the development of cervical and anal cancer (HPV-16). Aptamers are nucleic acid ligands derived from massively complex combinatorial libraries by a process of in vitro evolution, often referred to as systematic evolution of ligands by exponential enrichment (SELEX). Aptamers have the capacity to bind to important protein targets with high affinity and biological consequences including reducing viral infectivity. In this proposal we will test the following hypotheses: (1) Individual antiviral aptamers can be developed that demonstrate efficacy against HIV-1, HSV-2, and HPV-16 using in-vitro cell challenge experiments, (2) Antiviral efficacy can be demonstrated in cervico-vaginal, intestinal, and anal tissue explant systems and is not altered when aptamers are given as single agents or in combination, and (3) Combinations of antiviral aptamers can prevent infection of explant systems when multiple viruses are used in challenge experiments. The study will be undertaken by a consortium based at Oxford University (aptamer discovery), RNA-Tec (aptamer optimization and scale-up) and UCLA (tissue explant studies).